Chronic pain represents a major health problem in the world today. In many cases the generator for neuropathic pain appears to be in the peripheral nervous system. Thus delivery of gene vectors to primary afferents has potential to decrease pain. Manipulation of gene expression in dorsal root ganglion cells can also be used as a tool to understand better peripheral neural mechanisms of pain. The development of an effective gene therapy requires a multifaceted approach. These can be separated into three broad headings; 1) the choice of gene to be delivered, 2) the development of an ideal delivery vector, and 3) control of the expression of the delivered gene. Adenoviral vectors with improved neurotropism are being created by manipulating the fiber gene either by altering its natural tropism through genetic manipulation, or by using fibers from different adenovirus serotypes that have different cellular tropisms. Control of gene expression will be accomplished using a modified ecdysone system that allows tighter control of expression as compared to earlier versions. To enhance neuronal selectivity, we are constructing vectors that express the ecdysone receptors from a neuron specific promoter. Transduction of target cells (as well as non-target cells) will be monitored using sensitive techniques for tracking the viral vector in vivo. The genes we propose to examine are of two types. The first gene encodes the inwardly rectifying potassium channel, Kir2.1. Expression of Kir2.1 in neurons will reverse a salient change associated with neuropathic pain, namely increased excitability. We propose to measure the level of excitability using electrophysiological (patch clamp and other methods) and behavioral techniques. The other gene of interest encodes the alpha 2 delta calcium channel sub-unit. This protein appears to be crucial for the action of gabapentin, a drug that has been widely used in treating neuropathic pain in humans. In addition, alpha 2 delta is up regulated in at least one animal model of neuropathic pain. The effects of both increasing and decreasing alpha 2 delta expression will be monitored both in vitro and in vivo by a combination of electrophysiological and behavioral techniques. In conclusion, our proposal will look to combine improved vector development with novel recording techniques to monitor closely the efficacy of gene transfer and to also assess these treatments behaviorally in animals.